A 450-kyr record of hydrological conditions on the western Agulhas Bank Slope, south of Africa
A 450-kyr record of hydrological conditions on the western Agulhas Bank Slope, south of Africa
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DOI：
10.1016/s0025-3227(01)00213-4
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发表时间：
2002-02-15
期刊：
影响因子：
2.9
通讯作者：
Waelbroeck, C
中科院分区：
文献类型：
--
作者：
Rau, AJ;Rogers, J;Waelbroeck, C
非洲南部的阿古拉斯浅滩地区是一个重要而复杂的海洋区域。印度洋温暖的盐水泄漏到非洲南端周围的南大西洋是全球温盐环流的一个关键因素。有孔虫组合，稳定同位素和沉积学数据，从顶部10米的核心MD 962080，从西部Agulhas银行斜坡恢复，被用来表明在过去的450 kyr在南大西洋东南部的水团循环的变化。沉积学和浮游有孔虫数据给出了冷水侵入的明确信号。海底稳定同位素记录提供了地层框架，并表明最后四个气候循环（即下至海洋同位素阶段（MIS）12）。该化石群具有明显的向亚化石群过渡的特征，其中Globorotalia inflata和Neogloboquadrina pachyderma（右旋）是优势类群。输入冷，subanacitic沃茨到该地区通过泄漏通过亚热带辐合带，作为Agulhas环脱落的一部分，和一般冷却的表面沃茨的建议，发生在冰期的subanacitic组合。印度洋沃茨通过Agulhas海流的可变输入由热带/亚热带亚热带浮游有孔虫物种Globoquadrina dutertrei、Globigerinoides ruber（alba）和Globorotalia menardii的存在表示，最大泄漏发生在冰川末端。G.在整个地核中的menardii表明，在过去的450 kyr里，从南印度洋到南大西洋的水交换从未完全受阻。底栖碳同位素记录和沉积物结构数据反映了从北大西洋深水到南部上层组成水的核心位置的底层水团的变化。浮游有孔虫组合和沉积物组成表明，在MIS 7期间，大约200-250 kyr BP的核心站点的地表水条件发生了深刻的变化，从混合的亚南极洲和过渡水团到整体温暖的地表水条件。(C)2002 Elsevier Science B. V.保留所有权利。
The Agulhas Bank region, south of Africa, is an oceanographically important and complex area. The leakage of warm saline Indian Ocean water into the South Atlantic around the southern tip of Africa is a crucial factor in the global thermohaline circulation. Foraminiferal assemblage, stable isotope and sedimentological data from the top 10 m of core MD962080, recovered from the western Agulhas Bank Slope, are used to indicate changes in water mass circulation in the southeastern South Atlantic for the last 450 kyr. Sedimentological and planktonic foraminiferal data give clear signals of cold water intrusions. The benthic stable isotope record provides the stratigraphic framework and indicates that the last four climatic cycles are represented (i.e. down to marine isotope stage (MIS) 12). The planktonic foraminiferal assemblages bear a clear transitional to subantarctic character with Globorotalia inflata and Neogloboquadrina pachyderma (dextral) being the dominant taxa. Input of cold, subantarctic waters into the region by means of leakage through the Subtropical Convergence, as part of Agulhas ring shedding, and a general cooling of surface waters is suggested by increased occurrence of the subantarctic assemblage during glacial periods. Variable input of Indian Ocean waters via the Agulhas Current is indicated by the presence of tropical/subtropical planktonic foraminiferal species Globoquadrina dutertrei, Globigerinoides ruber (alba) and Globorotalia menardii with maximum leakage occurring at glacial terminations. The continuous presence of G. menardii throughout the core suggests that the exchange of water from the South Indian Ocean to the South Atlantic Ocean was never entirely obstructed in the last 450 kyr. The benthic carbon isotope record and sediment textural data reflect a change in bottom water masses over the core location from North Atlantic Deep Water to Upper Southern Component Water. Planktonic foraminiferal assemblages and sediment composition indicate a profound change in surface water conditions over the core site approximately 200-250 kyr BP, during MIS 7, from mixed subantarctic and transitional water masses to overall warmer surface water conditions. (C) 2002 Elsevier Science B.V. All rights reserved.